Oracle Enterprise Linux 5.6 fails to boot from multipath devices

Lately I've stared to work on a quite interesting Oracle Maximum Availability Architecture (MAA) project, with HP blades and Virtual Connect. From flexibility point of view the decision has been made to install operating system (Oracle Enterprise Linux 5.6) on a multipath LUN (no local hard drives).

The installer will find all multipath devices, generally the installation itself works fine. After reboot a surprise. During start up you will see on the console warnings about duplicate physical volumes, e.g.:

Found duplicate PV YAERKoTfbPGRMNdfyatZQU7cd3mt64Uc: using /dev/sdar2 not /dev/sdr2

then:

fsck.ext3: No such file or directory while trying to open /dev/mapper/mpath0p1...*** An error occurred during the file system check.*** Dropping you to a shell; the system will reboot*** when you leave the shell.Give root password for maintenance(or type Control-D to continue)(Repair filesystem) 1 #

A quick look at the initial ramdisk reveals missing files in the bin directory (e.g.: there are no bin/multipath) :

Thanks, I have a requirement to use OEL 5.6 and have been banging my head on the wall for about two days now trying to figure out why boot from SAN with DM-Multipath wasn't working. Rebuilt the initrd multiple times with multiple different modules. I didn't think to check to see if the multipath binary got loaded.